Packers are used in boreholes to isolate zones from each other. Typically these packers have a sealing system and slips that are radially extended on ramps referred to as slip cones for anchoring against the surrounding tubular. The setting of the packer can be accomplished hydraulically such as by dropping a ball on a seat and pressuring up the tubing which is communicated to a piston whose axial movement puts the packer in the set position. Another way such packers are set is with setting tools that are frequently run on wireline or slickline and the packer is set with relative movement of a setting tool. Typically the setting tool is releasably attached to the mandrel and has another component that bears on a setting sleeve to extend the slips and sealing assembly. When the set position is obtained, addition applied force from the setting tool shears a shear stud to allow the setting tool to release from the packer mandrel. The set position of such packers is usually retained by a ratcheting lock ring. The lock ring allows the setting movements initiated hydraulically or mechanically by the setting tool but the configuration of the ratchet assembly prevents a reversal of the setting movements thereby holding the set position.
In the past, if the packer is to be retrieved the ratcheting assembly was undermined by force that sheared a shear pin to allow the ratchet assembly to move to a release position so that the slips and sealing assembly could axially extend while radially retracting. Another way to release the packer without defeating the ratchet locking was to use a cutting tool and cut the packer mandrel clean through to allow the sealing assembly and slips to axially extend and radially retract for retrieval. As a last resort, the packer could be milled out with a milling tool driven by a downhole motor or a rotating string.
There have been designs that addressed the issue of packer release by forcing a disengagement of the ratchet profiles that allow relative movement in a first direction but prevent such movement in a reverse direction. In U.S. Pat. No. 7,080,693 the release occurs by penetrating through the mandrel wall with a penetration tool to access an annular chamber 80 for application of force to an axially moving release ring 66 that has spaced axially extending fingers 70 with leading ramps 72 as shown in FIG. 6. The axial movement under pressure in chamber 80 is designed to radially pry apart the ratchet patterns 56 and 58. This design uses a penetrator tool to release because in this packer application openings in the mandrel are considered not desirable because the packer mandrel is part of a pressure conducting tubular string. Apart from the inconvenience of running and locating the penetrating tool and then running pressure through the tool after penetration is the fact that fingers 70 move axially and are long and thin and subject to collapse if excessive force is required to separate the profiles on the mating locking rings.
Axial force is used to collapse a packer mandrel by radially pushing on a segment of the mandrel with a release tool that employs a collet running up a ramp to separate meshing profiles in the mandrel that are not ratcheting by moving a connecting segment radially. This design is shown in Doane U.S. Pat. No. 6,629,563. It releases in the same manner as packers that release with cutting the mandrel except that there is no destruction of parts with cutting tools.
Other designs employ axially movable sleeves to unlock mating parts of a lock assembly by converting the axial force into a radial force that overcomes a band spring biasing the locking segments toward the packer mandrel. This design is shown in U.S. Pat. No. 3,603,388. Here again designs that feature axial movement of thin sleeves or fingers can present problems if high forces are needed to dislodge the lock ring profiles apart and part failure could ensue.
What is needed and provided by the present invention is a release apparatus and method where the movement to separate the locking profiles is fully radial. In an application with a production packer that has a polished bore below to accept a production string there is no issue with mandrel openings that are above the sealing element of the packer. In such a packer the release tool operates through slots in the packer mandrel above the sealing element to radially displace locking ratchet segments that are radially biased inwardly. The release tool overcomes the bias to create a radial gap between the mandrel profile and the mating profile inside the segments so that the slips and sealing element of the packer can move axially and retract radially for recovery of the production packer. These and other aspects of the present invention will be more readily apparent to those of ordinary skill in the art from a review of the detailed description of the preferred embodiment and the associated drawings while understanding that the full scope of the invention is to be found in the appended claims.